Poor Man's Digital Dentist Core XY Build!

Hi guys.

LED's got me into Arduino, and Arduino got me into 3D printing. And now that I'm into 3D printing i've found a nice hobby.

Anyway, i am working on a coreXY machine with an approximate build platform of 18" cubed. For those of you who don't know, that is a large format printer. The gold standard prussa i3 has a build platform of around 8" cubed, for comparison.

My design is inspired and almost entirely coppied from The Digital Dentist's build over at RepRap.org. His printer is almost done, but I was so impressed with his build that I took at look at his pictures and I'm in the process of building an approximation.

He has access to a milling machine, and I don't, so had to make some sacrifices to account for this, but over all its looking good.

I thought this might be useful to Travis, since he is building a CNC machine and personally, i think a coreXY design lends itself to CNC as well as 3D printing.

I was able to finish a version of the effector mount. I haven't fully decided on my hotend it yet so there is definitely going to be changes.... im thinking about either dual e3dV6 or i've already a cyclops i modified to have water cooling. I want to do a direct drive (no bowden) system, however. I have might have some Nimble extruders for the cyclops, and if they get here and work that might be OK. The only issue is now i have a big printer and i really need a .8 nozzle or larger to make practical use of it and they are only available with e3d v6.

-Not bowden
-Dual Extrusion
-different nozzle sizes available

Would be my main criteria in that order. If anyone has any ideas on the front i'd appreciate it!

The motor mount didn't have enough "play" to get it to where i need to be in order to make the belts parallel, which is a requirement for coreXY printers, so i've got another one printing down that shifts the upper square over. derp. You can also see where i've added some mechanical stops to prevent the rail from sliding off the guides. Had that happen to me yesterday. Not again! (not a big deal, the rails have ball bearing retainers).

Thanks to The Digital Dentist for the idea of the belt mount.

Overall, the belts look parallel, which is good news. I'm waiting on the slowboat to get here for the larger pullys for the idler bearings... only option was to get them on aliexpress and wait forever. Well, unless you wanted to pay $15each for them. I've got an old RAMBO board hanging around so once i get the motor spacers reprinted i might fire it up and see how she chootches!. I've made some hole in the effector mount to attach a spare linear rail to so i can try the pencil thing DD did. I think that is a great way to check for backlash/optimum speeds, since you can easily see the ripple. Though, i expect with the hotend attached you might have to run a bit slower because of the added mass.

travis_farmer:
pic #3, get your dirty socks picked up before posting pictures

~Travis

Size calibration reference

I am using iko rails. I got them used on ebay for 30each. The sock is clean afaik, it's just dingy.

There is the belt path.

LinuxCNC supports corexy. The advantage of a corexy design is that you do not have to move the x axis motors when changing y position, and that allows greater speed at higher accuracy. My bed moves down for 3d printing, but you could also mount a motor on the effector to move the z position.

video

chootching away! Stepper whine is delightful

I put in a bigger bearing at the idler mount so the belts don't rub.

Parallel belts

Stepper whine is delightful

The bCNC program that I use has, in its tools menu, a program that turns MIDI music into Gcode. Play tunes on your CNC machine.

I filed down the edges so it's not as sharp as it looked. Only having access to a wood table saw and wood band saw the edges are a bit rough... but hey, you gotta piss with the dick ya got.

some reason the quote button ain't workin :-/..

but, travis, the mill was delivered already? How do you like it? What have you built with it. Any chance it would cut aluminum very slowly?

I think if your CNC can cut wood, it can hack metal Good enough for me. Who needs coolant when you got some nice chinese flutes and a couple cans of WD-40!

I got my first print out of my coreXY printer.

a perdy drawing

Most complicated 2D printer ever.

Nice work!

Just a small update today.

I got the endstops for x and y going. I am using hall effect sensors. I am planning to print a small cover to cover the sensors The wiring routes underneath the extrusion so that you don't have to see it

Once the printer is built i might turn off the less. All you gotta do is pull a jumper. They are pretty bright at 5v... but my final electronics will be duet Wifi and that runs at 3,3v.... so dimmer.

video

x and y don't need to be precise... but i'm going to print an enclosure which should stop them from getting knocked around accidently.

Nothing to write home about, but it should protect the Hall effect sensors... just clips onto the protoboard... Got some holes up to so I can see the end stops.

Some minor updates

I managed to mock up a cable carrier. I'm not sure if this one will have enough room to carry all the cables i need, but i bought multiple sizes so once i move into the wiring phase i'll make my decision.

One of the biggest changes is that i decided to go with 3" L bracket for a more roomier feel. It doesn't cost me any y space, but it might cost me some x space. I'm not 100% sure this is the final design but for the moment i like it. It allows me to mount my extruder and hotend right to the aluminum. For the extruder i am planning to use the Zesty Nimble which is a worm gear extruder and then a cyclops/chimera for the hotend. Initially i wanted to with two v6's... but with the chimera i can still get most of the larger nozzle sizes... and i already have a water-cooled cyclops in my delta. I might add watercooling to this printer too if needed, but i think with the wide open space for airflow under the hotend mount and the big hunk of alumninum, i might not need it. I'm only going to 50c in the enclosure.

I also changed how i routed the belts. I made basically a larger version of what was done on The Digital Dentist's corexy Z axis. It consists of a back plate, a center plate, and a front plate. The belts run through and are sandwiched together with six m3 screws. I have a peice of belt facing the opposite direction in each "tray" to help hold the belts. I'm not sure how this will work over time, but it seems like i got the belts a lot tighter using this method. In order to tighten the belts, i made the ends long so they fit all the way through the plates, then inserted a peice of belt along side the drive belt and pulled it though until everything was tight. Seems to work, but we will see how well everything handles being tugged on my motors soon.

I also started work on the z-drive. Nothing too crazy here... looks like it will work. Finally decided to invest in a nice set of metric taps, which made tapping the mounting holes a lot easier.

Another round of updates. I have figured out the z axis belt tensioning.

As you can see the bottom belt enters a printed block and then exits back out the bottom. I used another piece of belt along size to make sure it doesn't slip out. On the top, i have a screw and captive nut that pushes down on a block to pull the belt tight. I designed the part with some grooves so that it can't pop out. I didn't really have enough room for a belt along side the main belt where it exits (its there but only three teeth) so i zip-tied the belt together up top to stop it from slipping. It did not slip before i zip-tied it however. Over at it works

These are the things the belt pushes against. I put a bolt on the top where the other bolt pushes into this piece so that the plastic doesn't get worn or give as much. The little slot was for an alternate idea that didn't go anywhere :D. I was going to slide in a small washer and have the main screw hit that and feed through the plastic piece. This way is simpler and works.

Due to several factors i will need to redesign the hot end mount, as well as the x-rail. I am not happy with it ATM because it costs me too much y-space (3" almost) and i also need to be able to move it down about three inches. I think i will get another wider rail for the x axis and mount it in a more similar way to The Digital Dentists original design. In the end i may not go with the nimble because it creates about the same amount of problems as it solves. I bought it when i was committed to sticking with my Delta... was hoping i could repurpose it for the corexy but the drive cable will make an enclosure harder to design.

Figuring out the z-axis was so far the hardest part of the printer. I eventually settled on this set up. I had an extra 8mm rod, so cut it to length and mounted it to the top of the printer as you see. The pulley slides on the rod without a bearing. Its not the best, but i think for my purpose it will be OK. If not they do have some 5mm id 8mm od bearings. I can then get some 5mm rod and mount it in a similar way, with the bearing in-between the rod and pulley. Im up for other ideas as well.

I got the bed mount ready. The three black screws will be 50mm flat head screws that will be fed through the mic6 bed, with a spring, to allow me to level the bed. The aluminum blocks are tapped and there is a 6mm hole drilled through the extrusions to allow the screw to pass cleanly through without interference. I may need to beef this up, apparently the plate weighs 10 lbs!
Coming along.

ball screws are what a lot of people use, but i think with the steel belts and rails this design should work. If not i can add them later

Finally got the mill home and in place. I still have a lot of set up to do. I need to extend an existing 20amp 240v circuit so I can power the thing... and need to install the digital read out.

The mill and stand weighs around 1000lbs ;).

Edit: I forgot that I didn't mention my 3Dprintdr project was on hold until I got my mill set up.

Here is an update

This is the mount for the idler pulleys. I was using printed abs but after a month of tension in the belt the abs want really holding up, plus, i had to use long screws because the abs was thick...

A view from underneath, showing some pocketed fasteners.

This is the base of the motor mounts. The slots are to allow sideways adjustment of the motor, so that i can keep the belts parallel and at 90 degrees. I will cut slots in the aluminum tubing to tension the belts.

Just another view from the underside...

I really enjoy milling, got a lot to learn but there is something satisfying about shaping metal into something,

Got a few pictures of the mill set up with dro as well. A lot of chips..

I think ebay. is the best bed to get tooling, I got some nice end mills that are much higher quality than the grizzly set i bought for about half the price.... i want to get a corner-radius end mill set and maybe a face cutting end mill asap, but maybe after i get my small lathe.

travis_farmer:
slightly jealous of the mill. i may have to get one myself, when if i win the lottery...

You haven't been contacted by the "Nigerian National Lottery" about your win, yet? ? ? ?